Chapter 6 Applied Instruction API 1808 Symbol: S 1 ： Unit address Word S 2 ： Function code Word S 3 ： Device address Word S ： Register involved in the reading/writing of the data Bit/Word n ： Data length Word Explanation: 1. The operand S 1 should be within the range between 0 and 255. 2. S 2 : The function code For example: 1 (16#01): The AH500500 series PLC reads the data from several bit devices which are not discrete input devices. 2 (16#02): The AH500500 series PLC reads the data from several bit devices which are discrete input devices. 3 (16#03): The AH500500 series PLC reads the data from several word devices which are not input registers. 4 (16#04):
The AH500500 series PLC reads the data from several word devices which are input registers. 5 (16#05): The AH500500 series PLC writes the state into a bit device. 6 (16#06): The AH500500 series PLC writes the data into a word device. 15 (16#0F): The AH500500 series PLC writes the states into several bit devices. 16 (16#10): The AH500500 series PLC writes the data into several word devices. Only the function codes mentioned above are supported, and other function codes can not be executed. Please refer to the examples below. 3. S 3 : The device address If the device address is illegal, the error occurs. The error code is stored in the error log. 4. S :
The register involved in the reading/writing of the data The data which will be written into the external equipment is stored in the register in advance. The data which is read from the external equipment is stored in the register. 5. n : The length of the data The size of the data can not be larger than 240 bytes. For the communication commands related to the coils, the unit of the data is the bit, and n should be within the range between 1 and 1920.
For the communication commands related to the registers, the unit of the data is the 6-417 Instruction code Operand Function MODRW S , S , S , S, n 1 2 3 Reading/Writing the MODBUS data Device X Y M S T C HC D L SM SR E PR K 16# “$” DF S 1 S 2 S 3 S n Pulse instruction 16-bit instruction (11 steps) 32-bit instruction - AH500 -